In the simplest form, an organic electroluminescent (EL) device is comprised of an organic electroluminescent media disposed between first and second electrodes serving as an anode for hole injection and a cathode for electron injection. The organic electroluminescent media supports recombination of holes and electrons that yields emission of light. These devices are also commonly referred to as organic light-emitting diodes, or OLEDs. A basic organic EL element is described in U.S. Pat. No. 4,356,429. In order to construct a pixelated OLED display device that is useful as a display such as, for example, a television, computer monitor, cell phone display, or digital camera display, individual organic EL elements can be arranged as pixels in a matrix pattern. These pixels can all be made to emit the same color, thereby producing a monochromatic display, or they can be made to produce multiple colors such as a three-pixel red, green, blue (RGB) display. OLED display devices have also been fabricated with active matrix (AM) driving circuitry in order to produce high performance displays. An example of such an AM OLED display device is disclosed in U.S. Pat. No. 5,550,066.
When manufacturing organic EL displays, problems such a particle contamination or scratches in the organic EL materials can result in defects in a display. One type of defect that is caused by particle contamination or scratches is a short circuit through the thin organic materials, connecting the anode and the cathode. A short between the anode and cathode results in a non-emitting pixel (dead pixel) or a pixel that emits at reduced brightness (dim pixel).
A structure for improving robustness against shorting defects is described by Tyan et al. in U.S. Pat. No. 7,183,707. Tyan et al. describe inclusion of an inorganic short reduction layer disposed between the organic electroluminescent media and one of the electrodes. The short reduction layer has a particular electrical resistivity and thickness to reduce leakage current through a shoring defect. Several useful materials are described including Molybdium oxides as well as mixtures of partially conducting metal oxides with insulating oxides, fluorides, and sulfides.